Bio-oil production via co-pyrolysis of almond shell as biomass and high density polyethylene

•We investigate to see the effect of HDPE addition on thermal decomposition of lignocellulosic materials.•Increasing the proportion of HDPE in mixtures increases the oil yields.•After co-pyrolysis applied, obtained oil is more stable due to having lower oxygen content and higher heating value.•The addition of HDPE to aS has a positive effect on fuel properties of obtained oil.

Biomass from almond shell (aS) was co-pyrolyzed with high density polyethylene (HDPE) polymer to investigate the synergistic effects on the product yields and compositions. The pyrolysis temperature was selected as 500 °C, based on results of TGA-DTG. Co-pyrolysis of HDPE-biomass mixtures were pyrolysed with various proportions such as 1:0, 1:1, 1:2, 2:1 and 0:1. The yield of liquids produced during co-pyrolysis enhanced 23%, as the weight ratio of HDPE in the mixture was doubled. Obtained bio-oils were analyzed with using column chromatography, 1H NMR, GC/MS, and FT-IR. According to analyses results, produced liquids by co-pyrolysis had higher carbon (26% higher) and hydrogen contents (78% higher), lower oxygen content (%86 less) with a higher heating value (38% higher) than those of biomass oil.